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Water in Comets: A Target of Opportunity Proposal to Observe
Cometary OH

A. Wootten,(NRAO)
and Green Bank and Charlottesville REU Students

Water is the primary parent constituent of cometary atmospheres within 3 AU of the sun, but is normally unobservable or difficult to observe using earthbound telescopes. In the inner solar system, water escaping from the nucleus photodissociates, resulting in the production of the observable daughter molecule OH.

We propose to measure the water production rate in a bright newly discovered comet. This comet, C/1999 H1 (Lee), is a rich and productive comet, which will be entering southern skies accessible from Green Bank during late May. During that time, it will be optically visible at about magnitude 7.5. Using a formula due to Festou, we predict from this a water production rate of about 10 -29 mol s-1, one-third of P/Halley. From this we estimate that the OH lines would have an intrinsic strength of 0.3 K for the 1667 line, including a rough estimate of the Swings effect, which can extinguish the OH emission at certain relative velocities.

In addition to providing supporting data for other observatories, these observations will provide the summer students with a chance to gain observing and data reduction experience, produce a publishable result, as well as provide an introduction to some cometary science.

Photo of Comet Lee

Scheduling Parameters
1em #& #& #& #& #

Comet & LST Range & Transit & $\Delta$Ta & Datesb Name & & (LST) & (hours) &

C/1999 H1 (Lee) & 4h - 10h & 8h 48m & 4 & 22-25 May

a Approximate time needed for observation b Dates 1.6 GHz receiver is available

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Al Wootten